Stabilized aryl diazo-n-sulfonate light-sensitive material



Patented Got. 21, 1947 UNITED STATES Q STILIZED ARYL DIAZO-N- SULFONATE LIGHT-SENSITIVE MATERIAL N Drawing. Application September 15, 1943, Serial No. 502,466

This invention relates to the production of diazotype light sensitive layer wherein the lightsensitive agent is an aryl diazo-N-sulfonate and more particularly to the improvement of the stability and printing speed of such diazotype light sensitive layers.

Reproduction media for the photoprinting of transparent or semi-transparent originals in which media the photosensitive material is a diazo compound are well known. They are generally produced by treating the surface of a suitable base, such as paper, with a solution of two dye components, one of which, the diazo component, is the photosensitive body and the other, known as the azo component or coupling component, is a compound capable of reacting under suitable conditions with the diazo component to form a dye. The diazo component of such a light sensitive layer decomposes upon exposure to light to a compound which can no longer combine with the coupling component to form a dye. Thus, when a diazotype layer is exposed under an original tracing design, printed sheet or other work piece to be copied to a proper source of light, the diazo component in those areas which are not protected by the solid lines of the tracing or design or letters of the printed sheet is decomposed. Upon subsequent development, a dye forms only in the areas which are protected from the light by the solid lines of the tracing or design or letters of the printed sheet. The design of the original will thus be reproduced in color on a colorless background. The development of these diazotype light sensitive layers, wherein the light sensitive material is a diazo compound, is effected by contacting the exposed reproduction with a gaseous developing medium such as ammonia gas. Although developing apparatus has been made available in which to perform this operation wherein the development can be carried out with a minimum of leakage of ammonia gas, nevertheless, sufficient ammonia gas is absorbed by the paper to create an undesirable odor for some time after the development has been completed. Furthermore, it is often inconvenient and undesirable to store necessary supplies of ammonia water for the generation of the ammonia gas in the developing equipment on the premises.

In U. S. Patent 2,217,189 there is described a process of making positive photographic prints by the formation of an azo dye from dye components contained or produced in the light sensitive layer by a developing procedure which contemplates merely the contact of the photo ex- 5 Claims. (Cl; 95-7) suitable for further use.

. 2 posed light sensitive layer with heat. Since it is not necessary to employ ammonia or any other alkaline media to develop the light sensitive layers of that patent, the inconvenienceof storing ammonia water and the attendant disadvantages of the ammonia development no longer obtain.

This heat development process is based upon the use of such N-sulfonate diazo compounds as will completely decompose to non-coupling compounds upon exposure to light. The particular class of such diazo-N-sulfonates which are preferred for this function are the diazo-N-sulfonates which are derivatives of p-phenylene-diamines. It has now been found that the light sensitive layers obtained by coating a suitable base with a solution containing a diaZo-N-sulfonate of a p-phenylene-diamine and an azo component in accordance with the process of Patent No. 2,217,189 do not have as long a shelf life as the ammonia developable light sensitive layers coated with a solution of a diazo compound and an azo component. Furthermore, the coating solution is unstable and precipitates colored material after a short time which renders it un- This instability of the coating solution and shelf life of the coated paper can be improved by adding a quantity of sodium bisulfite to the coating solution as recommended in the patent. However, if sufficient 'sodium bisulfite is added to accomplish a commercially desirable stability and shelf life, the speed of printing by exposure to light is so retarded as to render the light sensitive layer unsuitable for any practical purpose.

We have now found that the coating solution can be sufficiently stabilized for all practical purposes and that the shelf life of the coated paper can be improved to an extent comparable with ammonia developable diazotype layers by adding ketones, ketonic acids or aromatic aldehydes or their substitution products, which will form addition products with bisulfites to the coating solution containing the diazo-N-sulfonate derived from a p-phenylene diamine, an

azo component and bisulfite. Where it is desirlight sensitive layer by adding at least molecularly equivalent amounts of the ketone, ketonic acid or aromatic aldehyde. Coating solutions which are stable for several days under ordinary ticularly adaptable to this process: Acetone, ketopentamethylene, cyclohexanone. acetonyl acetone, furfuraldehyde, levulinic acid, pyruvic acid, aceto acetic acid alkyl esters and benzaldehyde. It will be understood that the classification ketonic acids includes salts of such acids and their esters.

The following examples are illustrative of this invention, but are not intended in any way to limit the scope thereof. The parts are byweight unless otherwise specified.

Examples I. A coating solution was prepared by stirring into solutionin 1,000 cc. of water:

V Parts Diazo-N-sulfonate derived from 4-diethylamine-2-ethoxy aniline 9.3 Phloroglucinol 10.8 Thiourea 15.0 Sodium bisulfite 20.8 Benzaldehyde 21.2

A zinc acetate precoated paper was coated with the above solution and dried in the usual manner. Samples of this coated paper were then exposed to light. under adiapositive and the thus exposed sensitized samples were developed by contact with heat. Qther samples of the unexposed, but coated paper together with the exposed and developed samples were then stored for the purpose of determining the stability of the light sensitive layer of the finished print. Similar tests were made at the same time on the same type of paper coated with a solution containing the same components as above with the exception of thebenzaldehyde. It was observed that the printing speed and stability of the papers coated with. the solution containing the benzaldehyde were far greater than the printing speed and stability of papers coated with the same solutionlacking. the benzaldehyde. It was also observed that the background of the printed andheat developed coatings containing the benzaldehyde showed no discoloration after severalmonths storage whereas the printed and heat developed coating lacking the benzaldehyde developed considerable discoloration during the same period of storage.

11. A coating solution was prepared by stirring into solution in 1,000 cc. of water:

Zinc acetate precoated paper samples were coated with this solution and dried in the usual manner. The same tests were made as i th e Of Example 1 and the. results compared with the results obtained from a paper coated with the same solution but omitting the acetone. It was found that the stability and light sensitivity or printing speed of paper coatings made with the solution of this example have the same improved characteristics as compared with the characteristics of the paper coated with the same solution lacking the acetone as were observed in the case of. Example I.

Upon replacing the acetone of this example with 9.6- pts. of furfuraldehyde or molecular proportions of ketopentamethylene, eyclohexanone or aceto acetic acid ethylester light sensitive coatings having the same improved characteristics of stability and light sensitivity are obtained.

A coating solution was prepared by stirring into solution in 950 cc. of water:

Parts Diazo-N-sulfonate derived from 4-ethanol ethyl amino aniline 8.8 Thiourea g 15.0

Sodium bisulfite 10.4

Acetonyl ace e 10.0

To this solution there was added a solution of: 10.5 pts. of 2.3-dioxynaphthalene in 50.0 cc. of

isopropanol.

The resulting solution was coated on zinc acetate precoated paper and the coatings dried in the usual manner. Samples of these coatings were. then tested for stability'and sensitivity to light by exposing same'under a diapositive and developing the exposed light sensitive layers by heating. The thus exposed and developed prints and samples of unexposedcoatings were stored in the same manner as in Example I. It was found that the papers coated with the solution of this example had excellent characteristics as to stability and light sensitivity and showed a marked improvement over samples prepared from the same solution, but omitting the acetonyl acetone.

IV. A coating solution-was prepared by stirring into. solution in 950 cc. of water:

3 7 7 Parts Diaz o-N-sulfonate derived from 4-dimethyl aminoaniline 6.0 Thiourea 15.0 Sodium bisulfite 7.0 Sodium salt of pyruvic acid 8.4

To'this solution there was added a solution of: 8.0 pts. of aceto acetanilid in 50.0 cc. of isopropanoll The resulting solution was coated and dried on zinc acetate precoated' paper. Samples of this coated paper were then exposed to light under a diapositive and the resulting prints developed by heating. These printed and developed samples and samples of'unexposed coated paper were then stored for several months precaution being taken to prevent exposure of the unexposed samples during the storage period. Itwas found that the paper coated with the solution of this example was far superior in stability and light sensitivity of the unexposed coating and stability against discoloration of the exposed and developed coating when compared with similar coatings made without the addition of pyruvic acid sodium salt.

Upon substituting the sodium salt of levulinic acid for the pyruvic acid sodium salt of this example, the same improved coatings are obtained.

Having now particularly set forth and described our invention and having illustrated the best 5 method of performing it, what we now claim as new is:

1. A light sensitive layer on a suitable base comprising a mono diazo-N-sulfonate derivative of a p-phenylene diamine, an azo component, an alkali metal bisulfite, and a member of the group consisting of ketones, ketonic acids, and aromatic aldehydes Which form addition products withbisulfites.

2. A light sensitive layer on a suitable base comprising a mono diazo-N-sulfonate derivative of p-phenylene diamine, an azo component, and an addition product of an alkali metal bisulfite with a member of the group consisting of ketones, ketonic acids and aromatic aldehydes which form addition products With bisulfites.

3. A light sensitive layer on a suitable base comprising a mono diazo-N-sulfonate derivative of a p-phenylene diamine, an azo component, an alkali metal bisulfite and benzaldehyde.

4. A light sensitive layer on a suitable base comprising a mono diazo-N-sulfonate derivative of a p-phenylene diamine, an azo component, an alkali metal bisulfite and acetone.

5. A light sensitive layer on a suitable base comprising amono diazo-N-sulfonate derivative 01 a p-phenylene diamine, an azo component, an alkali metal bisulfite and pyruvic acid.

WILLIAM HENRY VON GLAHN. MAXIMILIAN K. REICHEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

